Background: In the emergency setting, acute abdominal pain is a diagnostic challenge, as pain is a subjective measure, and serious causes needing surgical intervention do not always meet the clinical picture. Biomarkers measuring the individual stress or pain level may aid in identifying surgical emergencies, but there are many influencing factors that have to be taken into account.

Objective: To evaluate defined stress biomarkers for their diagnostic and prognostic utility in measuring pain, and to evaluate potential influencing or confounding factors.

Design: Prospective observational study in 200 patients presenting to the emergency department with acute abdominal pain.

Estimated duration: May 2015 - May 2016 Location Setting: Emergency Department (ED) of the Hôpital Universitaire Pitié-Salpétrière, Paris, France.

Study population: 200 patients presenting to the ED with acute abdomen

Eligibility criteria:

• Inclusion criteria: Presentation at ED with acute abdominal pain, aged at least 18 years
• Exclusion criteria: no informed consent, pregnancy, homeless, no social assurance

Procedure:

Patients presenting to the ED with acute abdominal pain will be included after informed consent is given. Blood and saliva samples will be drawn initially and after 4 hours, and baseline data assessed. All diagnostic procedures results and diagnosis made by the treating physicians as well as initiated treatment will be recorded Final diagnosis and outcome will be assessed by 2-week-telephone interview.

Measurement of candidate biomarkers will be performed in collected material. Copeptin and SAA will be measured as potential biomarkers, as a control value, cortisol will be obtained. Other biomarkers will be in consideration, depending upon availability and financial aspects.

Safety evaluations: All recommendations outlined in the ICH Guidelines for Good Clinical Practice will be adhered to throughout this trial.

Sample size considerations: The number of patients of this pilote study is based on the estimate of 25 % or 50 of acute abdomen patients to have a surgical emergency.

Significance of the study: If a biomarker is found that safely discriminates between surgical urgency and harmless abdominal pain, this will spare radiologic exposure in often young patients and will aid in optimized allocation of health care resources.

Inclusion Criteria:

• Presentation at ED with acute abdominal pain, aged at least 18 years

Exclusion Criteria:

• No informed consent, pregnancy, homeless, no social assurance

patients presenting to the ED with acute abdomen